Metallurgical Investigation of a Turbine Blade and a Vane Failure from Two Marine Engines
The circumstances surrounding the in-service failure of a cast Ni-base superalloy (Alloy 713LC) second stage turbine blade and a cast and coated Co-base superalloy (MAR-M302) first stage air-cooled vane in two turbine engines used for marine application are described. An overview of a systematic approach, analyzing the nature of degeneration and failure of the failed components, utilizing conventional metallurgical techniques, is presented. The topographical features of the turbine blade fracture surface revealed a fatigue-induced crack growth pattern, where crack initiation had taken place in the blade trailing edge. An estimate of the crack-growth rate for the stage II fatigue fracture region coupled with the metallographic results helped to identify the final mode of the turbine blade failure. A detailed metallographic and fractographic examination of the air-cooled vane revealed that coating erosion in conjunction with severe hot-corrosion was responsible for crack initiation in the leading edge area.
A. K. Koul, R. V. Dainty, C. Marchand, Metallurgical Investigation of a Turbine Blade and a Vane Failure from Two Marine Engines, ASM Failure Analysis Case Histories: Offshore, Shipbuilding, and Marine Equipment, ASM International, 2019, https://doi.org/10.31399/asm.fach.marine.c9001657
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